The present disclosure relates generally to steering interchange systems in vehicles. In particular, steering systems where the vehicle switches from an all-wheel mode of steering to a second crabbing mode of steering through mechanical means are described.
Known steering interchange systems are not entirely satisfactory for the range of applications in which they are employed. For example, existing steering systems tend to be complex and require specialized components such as microprocessors, sensors, and complex electronic circuitry. In addition, not only are conventional steering systems more complex, but also more costly.
Thus, there exists a need for steering systems that are less complex and costly than the design of known steering mode changers/shifters. Examples of new and useful steering systems relevant to the needs existing in the field are discussed below.
Examples of references relevant to steering interchange system include U.S. Patent References: U.S. Pat. No. 6,371,243 to Donaldson (“Donaldson”), U.S. Pat. No. 7,278,511 to Gass (“Gass”), and U.S. Patent Application 20040129491 to Bean (“Bean”). The complete disclosures of the above patents and patent applications are herein incorporated by reference for all purposes.
Donaldson discloses a mobile personal lift that allows the operator to switch between different modes of steering. The Donaldson lift include directional switches and steering mode selectors that are coupled to a microprocessor that operatively coupled to hydraulic cylinders located at each wheel. The microprocessor controls the hydraulic cylinders corresponding to each wheel to the selected steering mode and corresponding movement of the joystick. Sensors positioned adjacent to each wheel and connected to the microprocessor measure the angular position of each wheel relative to the longitudinal axis of the chassis. The information from the sensors is then transmitted to the microprocessor and used to synchronize the wheels.
Gass also discloses a mechanism for switching between different modes of steering. Gass discloses one or more actuators for selectively steering wheels of the vehicle. Gass discloses an electronic control unit that provides control signal to one or more rear wheels. When the vehicle operator determines a particular steering mode is appropriate for the present riding conditions, an input device may be used to produce an input signal. A vehicle in accordance with the present invention, may also comprise an electronic control unit (ECU) coupled to a plurality of sensors. The ECU may compare a first riding parameter to a second riding parameter in order to determine whether operation in a second steering mode is appropriate, in light of present riding conditions. The ECU may produce an enabling signal when the ECU determines that operation in the second steering mode is appropriate for the present riding conditions.
Bean also describes a vehicle operable in a plurality of steering modes including two wheel steering, crab steer, and coordinated steer. A wheel angle sensor is disposed in coordination with each wheel. The Bean vehicle also includes a hydraulic cylinder coupled with extendable and retractable axles. The hydraulic cylinders may be controlled to effect extension and retraction of the axles only when the vehicle is traveling above a predetermined minimum speed. Four digital or analog switches are coupled with the axles indicating when the axles are fully extended. The drive and steering functions are controlled according to signals from the switches.